1. Field of the Invention
The present invention relates generally to methods and apparatus for delivering heat to hollow body organs. More particularly, the present invention relates to methods and devices for positioning a heat source within the interior of a hollow body organ.
In recent years, a variety of "least-invasive" surgical procedures has been developed as alternatives to conventional "open" surgery. While least-invasive surgical procedures have no fixed definition, they are generally characterized by use of specialized surgical tools in combination with visual or radiographic imaging techniques. The specialized tool is generally inserted through an open body orifice or a small surgical incision, and the tool is then positioned within the body using the imaging technique to allow manipulation of the organ or structure to be treated. A common example of least-invasive surgery is arthroscopic knee surgery, where penetration of the surgical tools is minimal. Less-accessible body organs, such as heart and interior blood vessels, may be reached by specialized catheters which may be routed through the vascular system over relatively long distances. Exemplary of such vascular catheters are balloon dilatation catheters which are used to expand regions of stenosis within diseased blood vessels.
Of particular interest to the present invention are least-invasive surgical techniques which rely on a catheter to deliver heat to the interior of a hollow body organ. As described in detail in co-pending application Ser. No. 07/407,839 and the delivery of heat may be used for deactivating or ablating a diseased body organ, such as a gallbladder, appendix, uterus, kidney, or the like, as well as for blocking other body lumens, such as blood vessels. Such catheters might also find use for other purposes, such as for thermal treatment of tumors, and the like.
The use of catheters to deliver heat internally within hollow body organs is problematic in certain respects. First, it can be difficult to properly position catheters at a desired location within a hollow body organ or adjacent connecting region. Such positioning difficulties can be exacerbated when the catheter includes a distal balloon for sealing such a connecting region in order to inhibit the loss of a thermally conductive medium which may be introduced to the body organ. For example, once the catheter tip is in place with the distal balloon inflated, it is difficult to reposition the catheter in order to relocate a heating element located on the catheter.
A second difficulty arises when using heating elements on the catheter, such as resistance coils, which are externally disposed in order to enhance heating efficiency. In that case, the catheter must be carefully positioned to avoid direct contact between the heating element and the inner wall of the hollow body organ. Direct contact can cause excessive heating, tissue adherence, and potential damage to adjacent body organs. The proper positioning of the catheter heating element relative to an entrapped fluid within the organ is difficult when the catheter is first placed within the hollow body organ and becomes more difficult as the catheter (and optionally a sealing balloon) is repositioned one or more times during a single treatment procedure.
For these reasons, it would be desirable to provide improved apparatus and methods for delivering heat to the interior of hollow body organs. It would be particularly desirable if catheters were adapted to facilitate positioning and repositioning of a heating element external to the catheter within the hollow body organ and were further adapted to provide for sealing of adjacent regions which connect to the hollow body organ. In particular, it would be desirable if the catheter heating element could be repositioned while an inflatable balloon remains in place to effect sealing of a region connecting with the hollow body organ. Desirably, the catheter will further include a shield arranged about the external heating element to prevent direct contact between the heating element and the interior wall of the hollow body organ. Desirably, such a shield may be movable in order to mix a fluid content of the hollow body organ to enhance temperature uniformity therein. Preferably, the catheter will be easy to manufacture, will provide access for introducing a thermally conductive medium into the interior of the hollow body organ, and will be suitable for distributing heat in a predetermined pattern within the hollow body organ and connecting region(s).
2. Description of the Background Art
Coleman, Non-Surgical Ablation of the Gallbladder, Proc. 1988 SCVIR, pp 214-219, is a review article discussing various techniques for non-surgical gallbladder ablation, including the work of Salomonowitz and of Getrajdman relating to the introduction of an externally heated medium to induce fibrosis of the gallbladder. The article further presents data demonstrating thermal ablation of a dog's gallbladder after open surgical injection of hot contrast media. The work of Salomonowitz is described in Salomonowitz et al. (1984) Arch. Surg. 119:725-729. The work of Getrajdman is described in Getrajdman et al. (1985) Invest. Radiol. 20:393-398 and Getrajdman et al. (1986) Invest. Radiol. 21:400-403. The use of sclerosing agents to induce gallbladder fibrosis is described in Remley et al. (1986) Invest. Radiol. 21:396-399. See also Becker et al. (1988) Radiology 167:63-68; Becker et al. (1989) Radiology 171:235-240; and Becker et al. (1989) Work in Progress Paper #1354, RSNA Meeting, November 1989. U.S. Pat. No. 4,160,455, describes a device for internally heating a body cavity for therapy, where the heat is intended to inhibit the growth of tumor cells. German Patent 37 25 691 describes a catheter combining a heater at its distal tip and a balloon proximate the heater, where the heater is not directly exposed to the fluid environment surrounding the catheter tip. U.S. Pat. No. 4,869,248, describes a thermal ablation catheter having a resistive heating loop at its distal end. Other patent documents describing heated or cooled catheters include U.S. Pat. Nos. 4,676,258; 4,638,436; 4,469,103; 4,375,220; 3,901,224; USSR 1329-781-A; and USSR 281489.